SM 25x275 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• Their magnetic field is durable, and after around ten years it decreases only by ~1% (theoretically),
• Magnets very well defend themselves against demagnetization caused by foreign field sources,
• Thanks to the reflective finish, the plating of Ni-Cu-Ni, gold-plated, or silver-plated gives an modern appearance,
• Magnetic induction on the top side of the magnet is impressive,
• Thanks to resistance to high temperature, they are capable of working (depending on the shape) even at temperatures up to 230°C and higher...
• Due to the option of precise molding and adaptation to custom solutions, magnetic components can be modeled in a wide range of forms and dimensions, which amplifies use scope,
• Fundamental importance in electronics industry – they are commonly used in data components, drive modules, precision medical tools, and other advanced devices.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

What to avoid - cons of neodymium magnets and ways of using them

• They are prone to damage upon too strong impacts. To avoid cracks, it is worth protecting magnets in special housings. Such protection not only protects the magnet but also increases its resistance to damage
• NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• Limited possibility of making threads in the magnet and complex forms - preferred is casing - mounting mechanism.
• Potential hazard related to microscopic parts of magnets can be dangerous, if swallowed, which is particularly important in the aspect of protecting the youngest. It is also worth noting that tiny parts of these devices can be problematic in diagnostics medical when they are in the body.
• Due to neodymium price, their price exceeds standard values,

Maximum holding power of the magnet – what affects it?

The load parameter shown represents the limit force, recorded under optimal environment, specifically:

• on a block made of structural steel, effectively closing the magnetic field
• whose thickness is min. 10 mm
• characterized by lack of roughness
• with zero gap (no paint)
• during pulling in a direction vertical to the mounting surface
• in stable room temperature

Impact of factors on magnetic holding capacity in practice

Real force impacted by working environment parameters, mainly (from priority):

• Gap (between the magnet and the plate), because even a microscopic clearance (e.g. 0.5 mm) leads to a reduction in lifting capacity by up to 50% (this also applies to varnish, corrosion or debris).
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the nominal value.
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of converting into lifting capacity.
• Steel grade – the best choice is pure iron steel. Stainless steels may attract less.
• Surface finish – ideal contact is obtained only on smooth steel. Any scratches and bumps reduce the real contact area, reducing force.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity testing was performed on a smooth plate of suitable thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the holding force is lower. In addition, even a small distance {between} the magnet and the plate reduces the lifting capacity.